Paper microfluidic analytical devices have emerged in recent years, leading to development of a number of inexpensive and quick point-of-care (“POC”) analyses, including HIV chips, paper ELISA, and other low-cost colorimetric diagnostic assays. Such paper microfluidic assays are gaining popularity as a simple and fast way of disease screening in resource limited environments. Although the colorimetric results of these assays can be viewed by naked eye, it is difficult to precisely quantify the analyte amount. Promising colorimetric detection results have been demonstrated using video cameras, digital color analyzers, scanners or custom portable readers. A key drawback of all these methods is the need for specialized instrumentation and for image analysis with a computer.
Mobile devices with wireless connectivity to remote computer systems, such as smart phones and tablets, offer attractive alternatives for imaging, analysis, and communication of results in the field. For example, with 6 billion mobile phone subscriptions worldwide, mobile phones are becoming ubiquitous. Indeed, several investigators have already demonstrated the use of phones in mobile phones for on-site diagnosis in dermatology, ophthalmology, and colorimetric diagnostics. However, mobile phones have yet to gain popularity for colorimetric detection due to three key challenges. First, integrated color balancing functions of a conventional mobile phone are optimized for photography in high ambient light, and are not suited for images when accurate quantitative measurements must be performed. Second, lighting conditions during imaging can be difficult to control, especially outside of a controlled environment like a laboratory. Third, analysis of images can be challenging especially when small color changes are present, and red, green, blue intensity (“RGB”) values alone are not necessarily sufficient. For these reasons, the use of cameras on mobile devices such as mobile phones and tablets has not yet been fully exploited for POC analyses.